GPS module for high altitude unmanned balloon
Hi, we've been looking for a GPS module to use in a high altitude balloon project and we've been able to find only two units (Lassen IQ and Trimble Copernicus) that follow the DoD spec correctly. Unfortunately both of them are a pain to use.
A GPS module should refuse to operate at an altitude of 60 kft AND airspeed of more than 999 knots, but in reality most commercial GPS modules implement these two rules with an "OR" operation.
If you know of any currently marketed GPS unit (preferably with a serial interface) that either joins these two limits with a conjunction ("AND") or implements just the speed limit with no regard for altitude, please link it here.
Thanks in advance :)
Replies to This Discussion
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Permalink Reply by Krzysztof Bosak on
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Permalink Reply by Evan Vincent Lane on -
Thanks Krzysztof!
Do you have any recommendations for one on this list that works well with the ArduPilot?
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Permalink Reply by Krzysztof Bosak on
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No, just found it on the Internet. I trust this data. Unfortunately I am not aware of +20kft GPS with 3-6Hz update rate.
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Permalink Reply by David on
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Check out this unit from Inventek (it is mentioned on the page that Krzysztof linked to). I've seen these fly to 110k' no problem, and Inventek is capable of working with folks interested in custom firmware, in fact, they list a number of "off-the-shelf" custom builds for their modules. Responsiveness depends on the agent that you talk to when you call.
I can vouch for the validity of the page that Krzysztof provided: the gentleman who put that together is an avid high-altitude hobbyist.
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Permalink Reply by David on
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By the way, there's a relatively simple explanation for the lack of high altitude support... 65535 is an easy number to settle on as a maximum, especially given that most applications don't require more than that.
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Permalink Reply by Scott Plunkett on -
The one David mentioned is your unit...it works well and has documented flights above 60k.
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Permalink Reply by David on
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Exactly: it's 2^16, a common memory block size that's easy to work with and results in a number that is greater than the number of feet that nearly all consumer GPS applications' altitude will ever hit. This results in a rather loose implementation of the GPS spec (OR logic rather than AND). Using the high-speed telemetry link that my team flew on high-altitude balloons, 65535 was commonly the last altitude seen when we tested limited receivers.
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Permalink Reply by marius3571 on
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The discontinued chip u-Blox TIM-LP works for sure. I've flown it up to 100,000. No idea about the newer u-Blox products.
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Permalink Reply by Yariv on
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From past experience with high altitude balloons, don't use Sirf !
It got stuck at 20km (even the time stopped) and only came back to life when we got below 18km.
The uBlox LEA-5H datasheet says that it works up to 50km.
They usually don't lie in their datasheets ;-)
I intend to use a uBlox module in the next balloon I build.
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Permalink Reply by Martin Seven on -
Thanks, in the end we went with the Copernicus - a bit older and a royal pain in the butt to work with, but known to operate well in near space.
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